Water Balance

On a yearly basis, Puerto Rico receives an average of 72 inches of rainfall, of which about 46 inches is lost to evapotranspiration, 23 inches is accounted as surface-water runoff, 1 inch is stored as surface water in reservoirs, 1 inch is withdrawn from coastal aquifers, and 1 inch is ground-water discharge from coastal aquifers and the seabed. Rainfall amounts and water balance vary across the Island. For example, the Ponce area (southwest) receive about 35 inches of rain each year, and evapotranspiration removes most of this rainfall. The offshore islands of Isla de Vieques and Isla de Culebra have a similar rainfall pattern as the south coast of Puerto Rico.

Average Water Budget for Puerto Rico